Acta Psychologica 150 (2014) 69–79

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Acta Psychologica

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Processingmorphologically complexwords in second-language learners:The effect of proficiency

Lijuan Liang, Baoguo Chen ⁎School of Psychology, Beijing Normal University, Beijing 100875, China

⁎ Corresponding author. Tel.: +86 10 5880 4071; fax: +E-mail address: Chenbg@bnu.edu.cn (B. Chen).

http://dx.doi.org/10.1016/j.actpsy.2014.04.0090001-6918/© 2014 Elsevier B.V. All rights reserved.

a b s t r a c t

a r t i c l e i n f o

Article history:Received 18 December 2013Received in revised form 17 April 2014Accepted 20 April 2014Available online xxxx

PsycInfo classification:2300

Keywords:Morphologically complex wordsL2 proficiencyRule-based decompositionWhole-word storageDeclarative/Procedural model

The present study explored how the processing of morphologically complex words in second-language (L2)learners changes as their proficiency increases. ERPs were recorded from highly proficient and less proficientL2 learners, using the repetition priming paradigm. Three experimental conditions were investigated: morpho-logical related/unrelated pairs, semantically related/unrelated pairs, and form related/unrelated pairs. The pres-ence of priming in each condition was assessed by comparing responses to targets preceded by related primeswith those preceded by unrelated primes. ERP results showed that highly proficient L2 learners demonstratedpriming effect within 350–550 ms in the morphological condition, associating with an N400 reduction, whileless proficient L2 learners showed nomorphological priming effectwithin the N400 range. Besides, formprimingeffect was observed in both highly proficient and less proficient L2 learners within 400–450ms and 450–500ms,and semantic inhibiting effectwas observed in both groupswithin 450–500ms, suggesting that less proficient L2learners were equally sensitive to the word form and meaning. The ERP results indicate that highly proficient L2learners manifest rule-based decomposition, while less proficient L2 learners relymore on lexical storage in pro-cessing morphologically complex words. Less proficient L2 learners have not developed the decomposing mech-anism, despite their sensitivity toword formandmeaning. Theway inwhichmorphologically complexwords areprocessed in L2 learners does change as their proficiency increases, validating the predictions of the declarative/procedural model.

© 2014 Elsevier B.V. All rights reserved.

1. Introduction

Morphologically complexwords serve as a peephole into the storageand processing ofmental lexicon and grammar (Ullman, 2005). Numer-ous studies have been carried out to investigate how morphologicallycomplex words are processed. According to the studies on nativespeakers, whether morphologically complex words are decomposedor stored in full form in themental lexicon depends onmany factors, in-cluding semantic transparency, regularity, imageability, and frequency(Prado & Ullman, 2009). To be more specific, reliable decomposition isfound in morphologically complex words that bear transparentsemantic relationship with their stems (e.g., “hunter”–“hunt”), butnot in those that bear opaque relationship (e.g., “corner”–“corn”)(Diependaele, Duñabeitia, Morris, & Keullers, 2011; Lavric, Rastle, &Clapp, 2011; Morris, Frank, Grainger, & Holcomb, 2007); regularinflected or derivedwords are often decomposed into stems and affixesin online processing, while irregular ones are stored in full form(Clahsen, 2006a; Lehtonen, Monahan, & Poeppel, 2011; Lück et al.,

86 10 5880 8187.

2006; Newman, Ullman, Pancheva, Waligura, & Neville, 2007); highimageability may facilitate the decomposition of morphologicallycomplex words (Prado & Ullman, 2009); low frequency inflected orderived words are often stored in full form (Bowden, Gelfand, Sanz, &Ullman, 2010; Clahsen & Neubauer, 2010). Recent findings show thatdecomposition occurs automatically at early stages of visual wordrecognition (Gold & Rastle, 2007; Lavric, Clapp, & Rastle, 2007). Morespecifically, decomposition is triggered when the surface structure ofcomplex words is processed (Bozic, Marslen-Wilson, Stamatakis,Davis, & Tyler, 2007).

Previous studies on morphologically complex words focused notonly on native speakers, but also on second-language (L2) learners.The situation for L2 learners, unlike native speakers, is more complicat-ed, because they are subject to the influence of additional factors includ-ing language exposure, their native language, and proficiency, besidesthe factors mentioned above (Babcock, Stowe, Maloof, Brovetto, &Ullman, 2012; Kirkici, 2007). The difference between native speakersand L2 learners in processing morphologically complex words hasbeen the focus of the previous studies. Various psycholinguisticmethods have led to consistent findings that native speakers tend to de-compose regular morphologically complex words in online processing(Clahsen, 2006a; Lehtonen et al., 2011; Lück et al., 2006; Newmanet al., 2007). On the contrary, evidence for L2 learners is highly

70 L. Liang, B. Chen / Acta Psychologica 150 (2014) 69–79

inconsistent. Diependaele et al. (2011) compared the performance ofnative English speakerswith that of Spanish–English andDutch–Englishbilinguals in a masked morphological priming lexical decision task. Theresults showed that bilinguals decomposed inflected words like nativespeakers did. Pliatsikas and Marinis (2012) compared highly proficientGreek–English learners with native English speakers in a self-pacedreading task involving past tense forms embedded in plausible sentences.The results showed rule-based decomposition in L2 learners. Contrary tothe above findings, Silva and Clahsen (2008) compared advanced adultEnglish learners with native English speakers in amasked priming lexicaldecision task. The results showed that the performance of L2 learnerswassignificantly different from that of native speakers, showing no morpho-logical priming for inflected and reduced priming for derived wordforms. L2 learners rely more on lexical storage in processing morpholog-ically complex words. Neubauer and Clahsen (2009) conducted a seriesof experiments including acceptability judgments, lexical decision, andmasked priming, and found that advanced adult second-languagelearners reliedmore on lexical storage andwere less sensitive to themor-phological structure than native speakers. Similar findings were also ob-tained in Clahsen, Felser, Neubauer, Sato, and Silva (2010). Therefore,existing evidence for L2 learners stands on two opposite sides. Onesupports the view that L2 learners can decompose regular inflected or de-rived words into their constituents like native speakers do (Diependaeleet al., 2011; Hahne, Mueller, & Clahsen, 2006; Kirkici, 2007; Pliatsikas &Marinis, 2012). The other supports the view that unlike native speakers,L2 learners rely more on lexical storage for morphologically complexwords (Clahsen, Felser, Neubauer, Sato, & Silva, 2010; Neubauer &Clahsen, 2009; Silva & Clahsen, 2008).

According to the declarative/procedural model (D/Pmodel) proposedbyUllman (2004, 2011a, 2011b), proficiencymaybe one key factorwhichdetermines whether L2 learners can decompose morphologically com-plex words like native speakers do. For the declarative/proceduralmodel, the twomemory systems of human cognition, declarativememo-ry and procedural memory, provide reasonable explanations for how lex-icon and grammar are processed in human language. More specifically,the declarative memory system underlies mental lexicon, and is particu-larly important in storing lexical knowledge (e.g., irregular inflected);the proceduralmemory system subserves grammatical structure buildingincluding the combination of stored lexical forms (e.g., regular inflected,“walk + -ed”) (Ullman, 2005). Grammar processing in native speakerslargely depends upon the procedural memory system, while L2 grammarprocessing relies on the declarative memory system initially at the lowproficiency level andmay come to rely on the proceduralmemory systemas proficiency increases (Morgan-Short, Faretta-Stutenberg, Brill-Schuetz,Carpenter, & Wong, 2013).

Hence, one reason for the inconsistent findings for L2 learners maylie in the distinct proficiency levels of the participants in previous stud-ies, because the declarative memory system may underlie the learningof lexical knowledge and rules of grammar initially, which allowswhole-word storage of complex words, and the processing will shiftto the procedural system with increasing learning abilities, allowingrule-based decomposition of complex words (Ullman, 2005). The de-clarative and procedural memory systems interact both cooperativelyand competitively in the acquisition and use of language (Ullman,2005). Therefore, it is not possible to draw an unequivocal conclusionon whether L2 learners are capable of native-like performance or notbased on evidence from a single homogenous group of L2 learners.The other reason may be that most previous studies on L2 learnersused behavioral measures, which are end-state measures, and less sen-sitive to online automatic cognitive processing than neurophysiologicalmeasures (Tokowicz & MacWhinney, 2005).

Until now, the specific effect of proficiency has not been well stud-ied. Although previous studies have selected highly proficient L2learners or those with longer exposure to L2 (Babcock, Stowe, Maloof,Brovetto, & Ullman, 2012; Neubauer & Clahsen, 2009; Pliatsikas &Marinis, 2012; Silva & Clahsen, 2008), the findings could not provide a

direct answer for the question whether the processing of morphologi-cally complex words in L2 learners changes with their increasing lan-guage proficiency.

To address the above issue of proficiency, the present study com-pared the processing mechanisms between highly proficient and lessproficient English learners whose native language is Chinese. Chineseis non-inflectional language while English uses inflectional morphology(Chu, 1982; Henne, Rongen, & Hansen, 1977). Cross-language similarityis believed to be an important factor that influences L2 morpho-syntactic processing (Ringbom, 2007; Tolentino & Tokowicz, 2011).The language distance of morphology between Chinese and Englishdoes not allow cross-linguistic transfer which is perceived betweenother languages (Morett & Macwhinney, 2013). Therefore, the impactof L1 was ruled out. Besides, both groups of participants were matchedon language exposure, sex, age, L2 learningduration, andworkingmem-ory span. Therefore, it was possible to explore the exact influence of pro-ficiency. According to the D/P model, less proficient L2 learners rely onthe declarative memory system initially and may come to rely on theprocedural memory system as their proficiency increases (Morgan-Short et al., 2013). Therefore, it can be predicted that highly proficientL2 learnersmanifest rule-based decompositionwhen processing regularmorphologically complexwords while less proficient L2 learners do not.

In the present study, N400 component was measured to evaluate theneural correlate of processing morphologically complex words. N400,previous shown to be sensitive to lexico-semantic information (Brown&Hagoort, 1993; Kiefer, 2002; Kutas & Federmeier, 2000), is also sensitiveto morphological decomposition as revealed in previous studies (Barber,Dominguez, & de Vega, 2002; Dominguez, de Vega, & Barber, 2004;Lavric et al., 2007, 2011; Morris et al., 2007; Morris, Grainger, &Holcomb, 2008;Münte et al., 1999). The amplitude of N400will be atten-uated when the stem word is processed (e.g., “walk”) if the prime (e.g.,“walking”) is decomposed into its constituents (e.g., “walk” + “-ing”),allowing a direct access to the stem word (“walk”). Besides, form (e.g.,“scandal”–“scan”) and semantic (e.g., “laughing”–“smile”) repetitionpriming effects also show N400 reduction, smaller in amplitude andshorter in latency than morphologically related pairs (e.g., “walking”–“walk”) (Brown & Hagoort, 1993; Holcomb, 1993; Lavric et al., 2007).The present study used the repetition priming paradigm which wasused in the studies of Münte et al. (1999) and Rodriguez-Fornells,Münte, and Clahsen (2002). All the primes and targets were available toconscious perception. Since morphologically related pairs often overlapin form and meaning, the prime and the target were separated by fourwords/nonwords which were inserted to minimize immediate form andsemantic priming effects. The intervening real-word fillers were notmor-phologically complex and bore no morphological, semantic and form re-lationship with the primes and targets. Furthermore, three experimentalconditions were included in the present study: morphologically related/unrelated pairs (“walking”–“walk,” “building”–“walk”), semanticallyrelated/unrelated pairs (“laughing”–“smile,” “laughing”–“bring”), andform related/unrelated pairs (“plant”–“plan,” “space”–“plan”). Both se-mantic and form conditions were included to examinewhether morpho-logical priming effect was indeed morphological in nature. If the N400attenuation induced by the morphological priming effect is larger thanthat of the form and semantic priming effect, it is possible to determinethat the morphological priming effect observed is indeed morphologicalin nature (Lavric et al., 2007).

Therefore, the present study aimed to explore whether the process-ing ofmorphologically complexwords in L2 learners changes with theirincreasing proficiency level. If the answer is yes, highly proficient L2learners would manifest rule-based decomposition represented by thepriming effect in the morphological condition when dealing with regu-lar inflected words, while less proficient L2 learners would not. In otherwords, we expect to observe larger N400 attenuation, which representsmorphological priming effect, in highly proficient L2 learners than inless proficient L2 learners, based on the predictions of the declarative/procedural model.

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2. Methods

2.1. Participants

Forty right-handed participants were selected from Beijing NormalUniversity. All were native speakers of Chinese (L1) who had began re-ceiving classroom teaching of English (L2) since middle school, andnone had been to the English-speaking countries before. All participantshad no history of hearing or language difficulties based on self-report.Data from9 participantswere excluded because of noisy EEG recordings(from high impedances or excessive eye/movement artifacts), resultingin 31 participants (14 female) in the final dataset. Fifteen participants(7 were female) were highly proficient L2 learners whose meanscore in the College English Test Band 6 (CET-6) was 578 (SD = 22),representing a high proficiency level. Sixteen participants (7 werefemale) were less proficient L2 learners, who failed once or even moretimes in the test (mean score=424, SD=27). The CET-6 test, designedby the Ministry of Education of China, is used in all universities in Chinato evaluate the English proficiency of non-English majors. It consists oftasks on listening comprehension, reading comprehension, vocabularyknowledge, grammar knowledge and writing. The total score is 710,and the cutoff point (set by the Ministry of Education) for success andfailure in the test is 427.

Themean age, duration of L2 learning,workingmemory span (WM),and second-language competency of both participant groups are pre-sented in Table 1.

Both groups were matched on age, duration of L2 learning, andworking memory WM) which was tested using operation span task(Unsworth, Heitz, Schrock, & Engle, 2005). Further test showed thathighly proficient L2 learners scored significantly higher in the grammarsection of Oxford Placement test (OPT) than the less proficient learners.The OPT test includes 25multiple choice questions and a cloze test, andthe total score is 50. Besides, the two groupswere significantly differentin L2 listening, speaking, and reading, but not in writing based on self-report in six-point scale assessment (1 for “quite poor,” 6 for “highlyproficient”).

All participants had normal or corrected-to-normal vision. Theyall signed the written informed consent, and were paid for theirparticipation.

2.2. Stimuli

Four hundred eighty prime-target pairs of English words were select-ed, including morphologically related/unrelated pairs (80 related, e.g.,“walking”–“walk” and 80 unrelated pairs, e.g., “building”–“walk”), se-mantically related/unrelated pairs (80 related, e.g., “laughing”–“smile”and 80 unrelated pairs, e.g., “laughing”–“count”), and form related/unrelated pairs (80 related, e.g., “plant”–“plan” and 80 unrelatedpairs, e.g., “space”–“plan”).

Morphologically related pairs bore a semantically transparent mor-phological relationship, while unrelated pairs bore no relationship atall. All the prime words for related and unrelated pairs took v-ingform which is recognized as typical inflection of words (Clahsen,2006b). Semantically related pairs bore a semantic relationship but nomorphological or form relationship, while unrelated pairs bore no rela-tionship at all. The mean semantic relatedness value for the semantically

Table 1Biographical information (standard deviations) for both participant groups.

Age Duration WM CET6

Highly proficient 23.4 (1.8) 10.2 (1.3) 41.1 (13.7) 578 (22)Less proficient 22.9 (1.6) 9.5 (1.4) 44.6 (15.7) 424 (27)

Note: The two groups were matched on age, duration of L2 learning, and working memory (d = 6.44), OPT (t(29) = 5.15, p b 0.001, Cohen’s d = 1.91), listening (t(29) = 3.39, p b 0.00(t(29) = 3.32, p b 0.005, Cohen’s d = 1.23), but not in writing (t(29) = 1.73, p = .09, Cohen

related pairs was 0.31 (SD = .15) assessed using the Latent SemanticAnalysis (LSA; Landauer & Dumais, 1997) web facility (http://lsa.colorado.edu) (1 for “very similar words” and 0 for “very dissimilarwords”), and 4.01 (SD = .62) assessed by 20 L2 learners using five-point scale (1 for “no semantic relationship” and 5 for “highly semanti-cally related”). The form related pairs bore an orthographic and phono-logical relationship but no morphological or semantic relationship,while unrelated pairs bore no relationship at all. The form relatedpairs shared the first three to five letters. The presence of priming ineach conditionwas assessed by comparing responses to targets preced-ed by related primes with those preceded by unrelated primes (Lavricet al., 2007, 2011; Münte et al., 1999; Rodriguez-Fornells et al., 2002).

The frequencies of the stimuli were calculated based on the frequen-cy dictionary of Brysbaert and New (2009), and the familiarity of thewords was assessed by a group of 30 L2 learners using five-point scale(1 for “don’t know” and 5 for “quite familiar”). More information forthe stimuli is presented in Table 2. Items for the related and unrelatedpairs in each condition were matched on word frequency, familiarityand length.

The stimuli were arranged in two lists, each containing 120 relatedand 120 unrelated pairs for the morphological, semantic, and form con-ditions. Therewere 40 related and 40 unrelated pairs for each condition.Moreover, each list contained 960 fillers, 720 of which were nonwords.The real-word fillers were not morphologically complex and bore nomorphological, semantic and form relationshipwith the primes and tar-gets. Therefore, half of the words in the list were real words, and theother half were nonwords. No item was repeated in the same formwithin the given list. Each participant saw one of the two lists. Thetask was to perform a lexical decision (word/nonword) for each word.

2.3. Procedure

All the trials were presented in random order across the threeconditions. Each word was presented for 800 ms, and the interstim-ulus intervals were varied randomly between 1600 and 2200 ms.Each prime-target pair was intervened by four words (both realwords and nonwords) which were randomly selected and classifiedas fillers to reduce immediate form and semantic priming effects.Participants were asked to perform a lexical decision (word/nonword)for each word, indicating their response by pressing one of two buttonson the keyboard. The assignment of response type to the left and righthands was counterbalanced across participants. The whole experiment(with 3 breaks) lasted for an hour.

2.4. Recording and analysis

Electroencephalogram (EEG) was recorded at a 1000-Hz samplingrate using a 64-channel NeuroScan net. Eyemovementsweremeasuredusing vertical (electrodes below and above the left eye) and horizontal(two electrodes placed lateral to the outer canthi of the two eyes) elec-trooculogram. The common EEG and electrooculogram (EOG) referencewas attached to the left mastoid, and re-referenced off-line to the meanof the activity at the left and rightmastoids. Electrode impedances werekept b5 Ω. The electrophysiological signals were filtered on-line with abandpass of 0.1–100 Hz and later low-pass (40 Hz) filtered off-line.

OPT Listening Speaking Reading Writing

42.5 (3.9) 4.6 (1.0) 4.1 (0.9) 3.8 (1.1) 3.9 (1.1)35.2 (4.0) 3.5 (0.8) 3.5 (0.5) 2.6 (0.8) 3.2 (1.2)

all ps N .05). They were significantly different in CET6 (t(29) = 17.26, p b .001, Cohen’s5, Cohen’s d = 1.26), speaking (t(29) = 2.39, p b 0.05, Cohen’s d = 0.89), and reading’s d = 0.65).

Table 2Mean frequency, familiarity and length (standard deviations) of the stimuli.

Prime type Relatedness Prime/Target Frequency Familiarity Length (letters)

Morphological Related Prime 35.16 (34.67) 4.79 (0.25) 7.68 (0.99)Target 170.37 (193.93) 4.73 (0.34) 4.75 (1.03)

Unrelated Prime 33.9 (29.14) 4.75 (0.27) 7.59 (0.96)Target 170.37 (193.93) 4.73 (0.34) 4.75 (1.03)

Semantic Related Prime 33.9 (29.14) 4.75 (0.27) 7.59 (0.96)Target 148.3 (330.3) 4.67 (0.39) 4.83 (1.13)

Unrelated Prime 33.9 (29.14) 4.8 (0.3) 7.59 (0.96)Target 170.37 (193.93) 4.73 (0.34) 4.75 (1.03)

Form Related Prime 83.48 (134) 4.5 (0.6) 5.5 (1)Target 164.77 (291.21) 4.38 (0.68) 3.53 (0.62)

Unrelated Prime 81.24 (55.49) 4.7 (0.5) 5.4 (0.6)Target 164.77 (291.21) 4.38 (0.68) 3.53 (0.62)

Note: Items for the related and unrelated pairs in each condition were matched on word frequency, familiarity and length (all ps N .05).

72 L. Liang, B. Chen / Acta Psychologica 150 (2014) 69–79

EEG data analysis was performed using Scan 4.3. ERPs time-lockedto the onset of targets were averaged off-line for each group of stimuli(targets of related and unrelated pairs in morphological, semantic, andform conditions) separately for each participant. Eye movements werecorrected by means of correlation. Epochs with EEG exceedingeither ±100 μV at any channel within intervals of 200 ms were au-tomatically rejected off-line. ERP data of all remaining trials wereincluded in the analysis. Epochs time-locked to targets onset wereextracted from −200 to 800 msec. Participants with b70% free of arti-fact epochs in one stimulus type were not included in the posterioranalysis. Altogether, nine participants were excluded.

The presence of priming in each condition was assessed by compar-ing ERP responses to targets preceded by related primes with thosepreceded by unrelated primes, manifesting a reduction of the N400component. For each participant group and condition, the mean ampli-tude of N400was derivedwithinfive 50-ms timewindows from centro-parietal electrodes (C3, CP3, CZ, CPZ, C4, CP4): 350–400 ms, 400–450 ms, 450–500 ms, 500–550 ms, and 550–600 ms. These electrodeswere chosen because N400 is typically observed in these sites whichare the strongest site of N400 effect without mingling with other com-ponents. The consecutive time windows of N400, which was also usedin the study of Lavric et al. (2007) and Lavric et al. (2011), allowed a de-tailed investigation of the cognitive timing differences between highlyproficient and less proficient L2 learners across the three conditions.Repeated-measures analyses of variance (ANOVAs) were run for eachof the above windows including factors the prime type (morphological,semantic, and form), relatedness (related and unrelated), laterality (leftlocation: C3 and CP3, central location: CZ and CPZ, right location: C4 andCP4), and proficiency (highly proficient and less proficient). Prime type,relatedness, and laterality were within-subjects factors, and proficiencywas a between-subjects factor. The main concern of the present studywas the presence of priming effect across the three conditions in thetwo participant groups. Therefore, only when reliable interactions in-volving relatedness were found, further analysis was performed. Signif-icance levels of the F ratios were adjusted with the Greenhouse–Geissercorrection and the corrected p values are reported.

3. Results

3.1. Behavioral results

Only reaction times for correct responses in the morphological, se-mantic, and form conditionswere included in the data analysis. Besides,reaction time outliers which exceed three standard deviation of themeanwere excluded fromdata analysis (1.4% of the data). Themean re-action times and accuracy in each condition for highly proficient andless proficient L2 learners are presented in Table 3, along with the reac-tion time and accuracy for nonwords.

Repeated-measures ANOVA was performed including factors theprime type (morphological, semantic, and form), relatedness (relatedand unrelated), and proficiency (highly proficient and less proficient).

The accuracy was quite high (ranging 91%–99%) for each participantgroup and condition. The accuracy of highly proficient learners evenreached 99% for targets in both related and unrelated pairs in the mor-phological condition. Comparedwith the less proficient group, the accu-racy for the highly proficient group was significantly higher in themorphological and semantic conditions (all ps b .01), and marginallyhigher for form unrelated pairs (p = .06).

With respect to the reaction time, significant main effect of primetype (F(2,58) = 19.05, p b .001, partial η2 = .39) and relatedness(F(1,29)= 5.78, p b .05, partial η2= .17), and pirme type× relatednessinteraction (F(2,58) = 41.85, p b .001, partial η2 = .59) were found.Follow-up analysis by prime type was performed, including factors re-latedness and proficiency. In the morphological condition, significantmain effect of relatedness was observed (F(1,29)= 38.24 p b .001, par-tial η2 = .57), indicating that both highly proficient and less proficientL2 learners demonstrated morphological priming effect. In the se-mantic condition, significantmain effect of relatedness was observed(F(1,29) = 44.39, p b .001, partial η2 = .6). Both groups respondedto the targets preceded by related primes much more slowly thanthose preceded by unrelated primes, resembling an inhibiting effect.In the form condition, significant relatedness × proficiency interac-tion was found (F(1,29) = 4.87, p b .05, partial η2 = .14). Furtheranalysis revealed significant priming effect for the highly proficientgroup (F(1,14) = 16.9, p b .01, partial η2 = .55), and no primingeffect for the less proficient group (F(1,15) = .43, p = .52, partialη2 = .03).

The analysis of the magnitude of priming showed that the main ef-fect of the prime typewas significant (F(2,58)= 38.52, p b .001, partialη2 = .57). Pairwise comparisons revealed significantly greater primingin the morphological condition than in the semantic condition(p b .001), and marginally significant priming in the morpholog-ical condition than in the form condition (p = .06). The magnitude ofpriming for the highly proficient group was greater than that for theless proficient group across all conditions (F(1,29) = 6.85, p b .05, par-tial η2 = .19). However, the correlation analysis showed that the profi-ciency scores in Oxford Placement test and CET-6 test did not correlatewith the magnitude of priming in the morphological (Oxford: r =.29, p = .1; CET-6: r = .22, p = .23), semantic (Oxford: r = .2, p =.27; CET-6: r = .28, p = .12), and form (Oxford: r = .27, p = .15;CET-6: r = .35, p = .06) conditions. The inconsistency of the resultsmay be due to the relatively small sample size. A larger samplesize, as required by the specified significance level of .05 and statisti-cal power of .8, may increase the significance level of the correlationcoefficients (Lachin, 1981).

As for nonwords, there was no difference between highly proficientand less proficient L2 learners in both reaction time (t(29) = .89,

Table 3The mean reaction times (RT, ms) (standard deviations) and accuracy (ACC, %) in the three experimental conditions for highly proficient and less proficient L2 learners.

Proficiency Morphological Semantic Form Nonwords

Related Unrelated Related Unrelated Related Unrelated

RT ACC RT ACC RT ACC RT ACC RT ACC RT ACC RT ACC

Highlyproficient

633 (109) 99.2 (1.5) 671 (126) 99.2 (1.3) 691 (146) 97.4 (3.3) 673 (127) 99.2 (1.3) 657 (140) 95.4 (4.5) 687 (167) 96.1 (2.9) 678 (47) 95.3 (15.6)

Lessproficient

622 (111) 97 (2.1) 648 (117) 95.9 (3.9) 683 (153) 91.1 (7.7) 649 (119) 95.9 (3.9) 644 (138) 92.6 (6.1) 652 (135) 93 (5.5) 714 (81) 90.2 (16.2)

73L. Liang, B. Chen / Acta Psychologica 150 (2014) 69–79

p = .38, Cohen’s d = − .55) and accuracy (t(29) = −1.5, p =.14, Cohen's d = .32).

3.2. ERP results

ERP results for highly proficient and less proficient L2 learners in themorphological, semantic and form conditions are presented in Figs. 1–3.

In the 350–400ms time window, analysis revealed significant maineffect of prime type (F(2,58) = 12.88, p b .001, partial η2 = .3) andlaterality (F(2,58) = 11.56, p b .001, partial η2 = .28), and significantprime type × proficiency (F(2,58) = 5.88, p b .01, partial η2 = .17),prime type × laterality (F(4,116) = 3.7, p b .05, partial η2 = .11),prime type × relatedness (F(2,58) = 4.09, p b .05, partial η2 = .12),and prime type × relatedness × proficiency (F(2,58) = 3.53, p b .05,partial η2 = .11) interactions. Follow-up analysis by proficiency was

Fig. 1. Grand average of ERPwaveforms of the targets preceded by related and unrelated primesand less proficient L2 learners.

performed, including factors of prime type, relatedness and laterality.For highly proficient L2 learners, significant pirme type × relatednessinteraction (F(2,28) = 4.54, p b .05, partial η2 = .24), but no reliablemain effect of relatedness (F(1,14) = 1.37, p = .26, partial η2 = .09)and prime type × relatedness × laterality interaction (F(4,56) =.92, p = .44, partial η2 = .06) were observed. Follow-up ANOVAs re-vealed marginally significant priming effect in the morphologicalcondition (F(1,14) = 4.47, p = .05, partial η2 = .24), while no reliablepriming effect was found in the semantic condition (F(1,14) = 3.21,p = .09, partial η2 = .19) and the form condition (F(1,14) = 3.04,p = .1, partial η2 = .18). However, for less proficient L2 learners,analysis revealed no reliable main effect of prime type (F(2,30) = 1.76,p = .19, partial η2 = .1) and relatedness (F(1,15) = .1, p = .75, partialη2 = .007), prime type × relatedness interaction (F(2,30) = 2.2, p =.13, partial η2 = .13), and prime type × relatedness × laterality

at the centro-parietal electrodes in themorphological condition for both highly proficient

Fig. 2. Grand average of ERPwaveforms of the targets preceded by related and unrelated primes at the centro-parietal electrodes in the semantic condition for both highly proficient andless proficient L2 learners.

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interaction (F(4,60)= .36,p=.77, partialη2= .02), indicating that prim-ing effect was not found in all the three conditions for less proficient L2learners.

In the 400–450ms time window, analysis revealed significantmain effect of prime type (F(2,58) = 5.79, p b .01, partial η2 = .17)and laterality (F(2,58) = 8.35, p b .01, partial η2 = .22), and primetype × relatedness interaction (F(2,58) = 5.07, p b .05, partial η2 =.15). Follow-up analysis by prime typewas performed, including factorsof relatedness, laterality and proficiency. In the morphological condi-tion, significant main effect of laterality (F(2,58) = 6.23, p b .01, partialη2= .17) and proficiency (F(1,29)= 4.91, p b .05, partial η2= .14), andmarginal significant relatedness × proficiency interaction (F(1,29) =3.78, p= .06, partial η2= .11)were found. Further analysis showed sig-nificant morphological priming effect for highly proficient L2 learners(F(1,14) = 5.07, p b .05, partial η2 = .26), while no morphologicalpriming effect was observed for less proficient L2 learners (F(1,15) =.56, p = .46, partial η2 = .03). In the semantic condition, no significantmain effect of relatedness (F(1,29) = 2.74, p = .11, partial η2 = .08),and interactions of relatedness × proficiency (F(1,29) = .1, p = .75,partial η2 = .004), relatedness × laterality (F(2,58)= .42, p= .66, par-tial η2 = .01), and relatedness × laterality × proficiency (F(2,58) =2.27, p= .11, partial η2 = .07) were found, indicating that no semanticpriming effect was observed for both highly proficient and less profi-cient L2 learenrs. In the form condition, only significant main effect ofrelatedness (F(1,29) = 9.37, p b .01, partial η2 = .24) and laterality(F(2,58) = 9.45, p b .001, partial η2 = .24) was observed, indicatingthat reliable form priming effect was found for both highly proficientand less proficient L2 learners.

In the 450–500ms time window, analysis revealed significant maineffect of prime type (F(2,58)= 7.19, p b .01, partial η2= .19), proficien-cy (F(1,29) = 4.66, p b .05, partial η2 = .14), and laterality (F(2,58) =14.74, p b .001, partial η2 = .34). Significant interactions of primetype × proficiency (F(2,58) = 3.88, p b .05, partial η2 = .12), andprime type × relatedness (F(2,58) = 4.81, p b .05, partial η2 = .14)were also observed. Follow-up analysis by prime type was performed,including factors of relatedness, laterality and proficiency. In themorphological condition, no main effect of relatedness (F(1,29) = .85,p= .36, partial η2 = .03), and interactions of relatedness × proficiency(F(1,29) = 2.33, p = .14, partial η2 = .07), relatedness × laterality(F(2,58) = .94, p = .39, partial η2 = .03), and relatedness × laterality ×proficiency (F(2,58)= .39, p= .67, partial η2= .01)were observed, indi-cating that no morphological priming effect was found for both highlyproficient and less proficient L2 learners. In the semantic condition, onlysignificant main effect of relatedness (F(1,29) = 5.03, p b .05, partialη2 = .15) and laterality (F(2,58) = 11.55, p b .001, partial η2 = .28)was observed. Both highly proficient and less proficient L2 learnersmanifested reliable semantic inhibiting effect. In the form condition,only significant main effect of relatedness (F(1,29) = 4.71, p b .05, par-tial η2= .14), and laterality (F(2,58)= 15.77, p b .001, partial η2= .35)was observed. Both highly proficient and less proficient L2 learnersmanifested reliable form priming effect.

In the 500–550ms time window, analysis revealed significant maineffect of prime type (F(2,58) = 16.6, p b .001, partial η2 = .36) andlaterality (F(2,58)= 20.37, pb .001, partial η2= .41), andmarginal effectof relatedness × laterality × proficiency interaction (F(2,58)= 3.21, p=.05, partial η2 = .1). Further analysis only revealed significant priming

Fig. 3. Grand average of ERP waveforms of the targets preceded by related and unrelated primes at the centro-parietal electrodes in the form condition for both highly proficient and lessproficient L2 learners.

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effect in the morphological condition at the central electrodes for highlyproficient L2 learners (F(1,14) = 5, p b .05, partial η2 = .26). No reliablepriming effect was found in the semantic and form conditions for highlyproficient L2 learners at all electrodes (all ps N .05), and no reliable prim-ing effect was found across all the three conditions for less proficient L2learners at all electrodes (all ps N .05).

In the 550–600 ms time window, the main effect of relatedness(F(1,29) = .6, p= .44, partial η2 = .02), and all the interactions involv-ing relatedness were not significant (all ps N .05), indicating that no re-liable priming effectwas found in all the three conditions for both highlyproficient and less proficient L2 learners.

On the whole, for the highly proficient group, priming effectreflected by N400 attenuation was found in the morphological con-dition within 350–400 ms, 400–450 ms, and 500–550 ms, whileN400 attenuation in the form condition was found only within400–450 ms and 450–500 ms. Significant N400 enhancement wasfound for the semantic conditionwithin 450–500ms. For the less profi-cient group, no morphological priming effect was observed across allthe time windows, while form priming effect was found within 400–450 ms and 450–500 ms, and semantic inhibiting effect was foundwithin 450–500 ms. N400 change across the five time windows ineach condition for both participant groups was reflected in the differ-ence waves (related minus unrelated) (see Fig. 4) and the topographicmap (see Fig. 5).

Furthermore, correlation analysiswas conducted betweenproficien-cy scores and the magnitude of ERP priming in the morphological, se-mantic and form conditions. The proficiency scores used participants'scores in Oxford Placement test and CET-6 test. The magnitude of ERP

priming in the three conditions was derived from the differencewaves at the central electrodes in each condition. More specifically,the magnitude of morphological priming was the mean amplitude ofthe difference waves within 350–550 ms in the morphological condi-tion; the magnitude of semantic priming was the mean amplitude ofthe difference waves within 450–500 ms in the semantic condition;the magnitude of form priming was the mean amplitude of the differ-ence waves within 400–500 ms in the form condition. The above timewindows were chosen because significant priming effect was found inat least one participant group within these time windows. Resultsshowed that proficiency significantly correlated with the magnitudeof morphological priming (Oxford: r = .35, p b .05; CET-6: r = .43,p b .05). Participants with higher level of L2 proficiency manifestedlarger morphological priming effect. However, proficiency did notcorrelate with the magnitude of semantic priming (Oxford: r = .24,p = .19; CET-6: r = .15, p = .41) and form priming (Oxford: r =.09, p = .63; CET-6: r = .22, p = .23).

4. Discussion

The main goal of the present study was to explore whether the pro-cessing ofmorphologically complexwords changeswith the proficiencylevel of L2 learners. More specifically, this study examined whetherhighly proficient and less proficient L2 learners are different in process-ing morphologically complex words.

Behavioral results showed that both highly proficient and less profi-cient L2 learners manifested morphological priming in reaction times.Highly proficient L2 learners also exhibited priming effect in the form

Fig. 4. Difference waves (related minus unrelated) at the centro-parietal electrodes in the morphological, semantic, and form conditions for both highly proficient and less proficient L2learners.

76 L. Liang, B. Chen / Acta Psychologica 150 (2014) 69–79

condition, while the less proficient L2 learners did not. Both participantgroups exhibited inhibiting effect instead of priming effect in the se-mantic condition. The analysis of themagnitude of priming showed sig-nificantly greater priming in the morphological condition than in thesemantic condition, and marginally significant priming in the morpho-logical condition than in the form condition. The magnitude of primingfor the highly proficient group was greater than that for the less profi-cient group across all conditions. However, proficiency did not correlatewith themagnitude of behavioral priming effect in the three conditions.

Fig. 5. Topographicmaps of the priming effect (relatedminus unrelated)within different timewless proficient L2 learners.

The possible reason for this may be the small sample size which is notlarge enough for the specified significance level and statistical power.Reliable proficiency effect may be found using a larger sample size.Contrary to the behavioral results, ERP findings showed that highlyproficient L2 learners exhibited priming effect in the morphologicalcondition within 350–400 ms, 400–450 ms, and 500–550 ms, whileno morphological priming effect was observed across all the time win-dows in less proficient L2 learners. Both highly proficient and less profi-cient L2 learners showed form priming effect within 400–450 ms and

indows in themorphological, semantic, and form conditions for both highly proficient and

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450–500 ms, and semantic inhibiting effect within 450–500 ms. Profi-ciency significantly correlatedwith themagnitude of ERP priming effectin the morphological condition, while the correlation between profi-ciency and the magnitude of ERP priming effect in the semantic andform conditions was not significant. The inconsistency between behav-ioral and ERP results was also observed in other studies (Kiefer &Brendel, 2006; Landi & Perfetti, 2007; Qu, Damian, & Kazanina, 2012;Thierry &Wu, 2007). The reason why this occurred may be that behav-ioral and ERP measures capture different aspects of information pro-cessing. ERPs reflect implicit and moment-by-moment processing(Tokowicz & MacWhinney, 2005), while RTs are, by their nature, end-state measures, unable to tract moment-by-moment processing(Kutas & Federmeier, 2011). The ERP technique excels in temporalresolution and precision in detecting brain activity, making it possibleto determine which stage is being affected (Luck, 2005). Therefore,ERP measure is more sensitive than behavioral measure (Tokowicz &MacWhinney, 2005), especially for investigating the developing linguis-tic competence of adult L2 learners (McLaughlin, Osterhout, & Kim,2004). The combination of behavioral and ERP measures may avoid er-roneous conclusions. The primary focus of the present study is on thecognitive processing differences between highly proficient and less pro-ficient L2 learners. Therefore, the discussion was mainly focused on theERP findings.

ERP results showed that highly proficient L2 learners demonstratedpriming effect within 350–550 ms in the morphological condition,which occurred earlier and lasted longer than the priming effect in theform condition. This is consistent with the findings in the study ofLavric et al. (2007), who observed morphological priming effect in the340–500 ms range and form priming effect in the 380–460ms range.Moreover, inhibiting effect was found in the semantic condition within450–500ms. Therefore, the priming effect of the morphological proper-ty of the words was different from that of form and semantic priming,andwas indeedmorphological in nature. Themorphological priming ef-fect could not be attributed to the semantic and form overlap betweenprimes and targets.

In the morphological condition, when the related morphologicalpairs were presented, the prime “walking” was decomposed into“walk” and “ing,” leaving a trace in the episodic memory which facili-tates the access of the target “walk,” hence leading to an attenuatedN400 component. However, less proficient L2 learners showed no prim-ing effectwithin theN400 range. For them, the prime “walking”was notdecomposed, hence no facilitation to the access of the target “walk”occurred. Therefore, highly proficient L2 learners manifested rule-based decomposition when processing regular morphologicallycomplex words, while less proficient L2 learners did not. Less profi-cient L2 learners relied more on lexical storage and memorization.Overall, proficiency is a significant factor in morphological decompo-sition, which is supported by the significant correlation betweenproficiency scores and morphological priming effect observed inthe present study.

These findings shed light on the previous disputes over the inconsis-tent findings concerning L2 learners. The disagreement on whether L2learners can achieve native-like rule-based decomposition or notwhen processing regular morphologically complex words could be re-solved if proficiency is taken into consideration. Proficiency is one ofthe factors modulating how morphologically complex words are proc-essed in L2 learners whomay achieve native-like processing eventuallyso long as they attain the appropriate proficiency level. Participants inprevious studies may have distinct L2 proficiency levels, leading to in-consistent results, some of which support that L2 learners manifestnonnative-like whole-word storage (Clahsen, Felser, Neubauer, Sato, &Silva, 2010; Clahsen & Neubauer, 2010; Neubauer & Clahsen, 2009;Silva & Clahsen, 2008), while some support that L2 learners can achievenative-like rule-based decomposition (Diependaele et al., 2011; Hahneet al., 2006; Pliatsikas & Marinis, 2012). Findings in this study also pro-vide evidence to the predictions of the declarative/procedural model,

which claims that L2 beginners rely more on the declarative memorysystem and may come to rely on the procedural memory system at ahigh-level of proficiency (Ullman, 2005).

The proficiency level of L2 learners is a dynamic process or a contin-uum (Sparks, 2009), along which L2 learners' word processing mecha-nism may be changed from less efficient to highly efficient. Wordaccess involves three distinct levels: the conceptual level, lemma level,and lexeme level (Caramazza, 1997). The conceptual level representslexical concepts, the lemma level represents syntactic/semantic featureof the lexical item, and the lexeme level represents phonological and or-thographic representation of words. Information at each level is activat-ed, spread, and retrieved across nodes at different levels. Changes mayoccur at the lemma level for morphologically complex words as L2learners’ proficiency grows. At first, all morphologically complexwords are stored in the mental lexicon as separate lemmas mappingonto their own lexemes. The activation of orthographic and phono-logical information is spread along the single route to the designatedlemma. At a high level of proficiency, one may have acquired the ruleof decomposition governing the words through statistical learning(Frost, Siegelman, Narkiss, & Afek, 2013), and starts to store “walk,”“-ed,” “-ing,” and “-s” separately as distinct lemmas. Therefore, theactivation of orthographic and phonological information is spreadalong two routes to retrieve the words “walk-ing,” “walk-ed,” and“walk-s”. In this way, more words are derived through the integra-tion of stems, prefix, and suffix. The reason why the change at thelemma level occurs only when one's L2 attains a high level of proficiencymay lie in that the functional brain connectivity in the language network,especially total, between- andwithin-network integration levels, chang-es as L2 proficiency increases, reflectingmore automatic processingwithlow cognitive effort and attention (Saidi et al., 2013; Segalowitz &Hulstijn, 2005).

With regard to the form condition, results showed significant formpriming effect within 400–450 ms and 450–500 ms in both highly pro-ficient and less proficient L2 learners. Theywere equally sensitive to theorthographic information presented. Also, both exhibited inhibiting ef-fect within 450–500ms in the semantic condition instead of priming ef-fect. The reason why this occurred may be that for semantically relatedpairs “laughing”–“smile,” the prime “laughing” left a semantic tracewhich is not the exact one the target “smile”would activate. Therefore,the trace left by the prime did not facilitate the semantic retrieval of thetarget, especially when there was a four-word lag between the primeand target. On the whole, less proficient L2 learners performed equallywell in the form and semantic conditions except themorphological con-dition, suggesting that they have not developed the decomposingmechanism in processing regular morphologically complex words de-spite their sensitivity toword form andmeaning. Indeed, change in cog-nitive processing and brain connectivity is modulated by L2 proficiency(Saidi et al., 2013).

The current study recruited highly proficient and less proficient L2learners whose L2 proficiency did not overlap at all. Even though thepresent study revealed significantly different morphological processingmechanisms between the two groups, the dynamic trend of change incognitive processing mechanism with increasing levels of proficiencycould not be observed. Further studies on this matter may take profi-ciency as a continuous factor.

One limitation of the present study is that the four interveningwords may have some influence on the target words followed. Never-theless, we have minimized the influence. First, the four interveningwords included not only real words but also nonwords. The 240 real-word fillers were not morphologically complex and bore no morpho-logical, semantic and form relationship with the 240 target words.Additionally, the presence of nonwords could weaken the possible in-fluence of the intervening words on the target words followed. Second,the selection of intervening words in the presentation of stimuli wasrandomized. The intervening words for each trial were not fixed, andwere different across all participants. Therefore, the influence of the

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possible relatedness between real-word fillers and the target wordswas kept to a minimum.

5. Conclusion

In summary, the present study demonstrated the exact influence ofproficiency in modulating the way regular morphologically complexwords are processed in L2 learners. Highly proficient L2 learners mani-fest rule-based decomposition, while less proficient L2 learners relymore on lexical storage. These findings not only validate the predictionsof the declarative/procedural model, but also support the claim that L2learners will eventually achieve native-like processing mechanism aslong as they attain the appropriate level along the continuum ofproficiency.

Acknowledgments

This research was supported by the National Social Science Fund[11BYY039], the Fundamental Research Funds for the Central Universi-ties, and the Program for New Century Excellent talents of Ministry ofEducation of China [NECT-11-0028], and Beijing Key Lab of Applied Ex-perimental Psychology to Baoguo Chen.

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